No trick .... it was just a very old save from a point where it was still possible to do this.

You can't do this anymore. Was a bit naughty of Xoc to use that in a video really as it did give the impression that this was something you could do. Only the 'non suspension' wheels can have anything attached to them.

What the mod is doing is putting an attachment point on the outside of the wheel spawned with the suspension. You can attach anything to the wheel....I tried it after GrindyGears posted the link.

Works fine for cosmetic purposes, but the properties of the added on wheel are just those of the block, and the wheel that is part of the suspension setup has to still be there. It will still bounce up and down with the parent wheel. Strength will be unchanged, as the wheels break off the axles...and nothing has changed there. You are not attaching different wheels to the suspension, you are adding things to an attachment point on the outside of the existing wheel.

What you also have to watch for is the fact that making wheels wider can lead to grip issues on rough terrain. There is no flex or give in the tyres, so unlike real world 'balloon' tyres, your super wide tyres can run into issues.